1. Field of the Invention
This invention relates to a stepping motor driving system for driving a stepping motor used in a printer, a copying machine, a robot or the like, and a process for driving a stepping motor.
2. Description of the Prior Art
In an example of conventional stepping motor driving systems, motor supply current is passed through a motor coil until a coil current detection value reaches a upper limit set point. When the coil current detection value has reached the upper limit set point, motor regeneration current is passed through the motor coil until first predetermined time elapses. When the first predetermined time has passed, motor reflux current is passed through the motor coil until second predetermined time elapses since the motor supply current begins to pass through the motor coil. When the second predetermined time has passed, the motor supply current is passed through the motor coil until the coil current detection value reaches the upper limit set point. When the coil current detection value has reached the upper limit set point, the motor regeneration current is passed through the motor coil until the first predetermined time elapses. Thereafter, the same control is performed.
In another conventional stepping motor driving system, motor supply current is passed through a motor coil until supply time that corresponds to a supply time signal elapses. When the supply time has passed, motor regeneration current is passed through the motor coil until fixed regeneration time that corresponds to a regeneration time signal passes. When the regeneration time has passed, motor reflux current is passed through the motor coil until predetermined time elapses since the motor supply current begins to pass through the motor coil. When the predetermined time has passed, the motor supply current is passed through the motor coil until the supply time elapses. When the supply time has passed, the motor regeneration current is passed through the motor coil until the regeneration time passes. Thereafter, the same control is performed.
However, in such stepping motor driving systems, time that the motor reflux current flows becomes constant, so that there is a possibility that distortion in the coil current is increased at a certain rotation speed and a ripple current is increased. Therefore, a vibration of the motor is increased, high-speed response characteristics are deteriorated and a step angle precision in a micro step is decreased. In particular, when digitizing processing-control is performed, such problems are noticeable.